It is also reviewing how its own in-house department provides services to its half a million members.

Details of the planned overhaul of the union's legal services have been put to its management in a paper by Bruce Piper, the legal department head.

Piper says there is no immediate plan to drop firms. “We are sending out the code of practice for their (lawyers') comments. In the next 12 months we will take these into account when considering how to rationalise the service.”

But as to whether Unison will reduce the number of firms used, Piper says: “Eventually I think that will probably be so.”

The Unison code of practice will look at charging practices, speed in dealing with correspondence, quality assurance matters and advising on merits of cases. One proposal is that Unison would not expect to pay for cases which have a less than 50 per cent chance of success. Firms would be able to concentrate on stronger cases.

Union members will benefit by having a clearer idea of what services they can expect from the lawyers, says Piper.

The panel deals with the bulk of personal injury cases, with the in-house team handling much of the union-and employment-related work.

Rationalising the legal panel would be in keeping with the current trend among other large unions, which are all looking for more cost-effective and and efficient provision of services at a time of generally decreasing memberships.